Cylindrical or cup (crucible) shape ceramic articles of rare earth oxides or fluorides are generally prepared by molding methods including mold pressing, rubber pressing (or isostatic pressing), slip casting, and doctor blade methods. There is furnished rare earth oxide powder for a particular molding method. The powder is molded into ceramic compacts of cylindrical or cup shape by any molding methods. The compacts are subjected to firing, sintering and working steps until they are finished into products of the predetermined size. Molded articles of heat-resistant metals, typically tungsten (W) are similarly prepared.
However, where it is desired to produce thin-wall articles, especially having a thickness of up to 5 mm, the standard molding methods are difficult to produce acceptable molded articles because cracking occurs during the molding step. One common solution to this problem involves molding compacts having a greater thickness so as to ensure higher yields of compact formation, firing and sintering the compacts, and grinding or otherwise machining the compacts to a wall thickness of up to 5 mm.
This method, however, is disadvantageous in that as the final article becomes thinner in wall thickness or greater in volume, the method requires a more amount of source material and a longer time for product finishing. Because of cracking and warpage during sintering, the yield of overall manufacture is substantially reduced, resulting in an increased cost. This is a problem in the manufacture of ceramic or metal articles.